In general, a construction machine is driven by using a hydraulic pressure. The hydraulic pressure is supplied from one or more hydraulic pumps operated by an engine. The hydraulic pumps pressure working oil and supply the pressured working oil to respective actuators. The working oil is properly distributed to the actuators via a distributor called a main control value.
An output of the engine is lost while the working oil passes through hydraulic parts, such as a pump, a pipeline, a valve, a main control valve, for driving a hydraulic pressure. The actuators are operated at an efficiency of approximately 20% of the engine output.
In recent years, studies on pump control systems equipped with pumps for supplying working oil in correspondence to respective actuators to increase an efficiency of a hydraulic system for an output of an engine are being conducted.
Such a pump control system is designed such that pumps driven by an engine directly supply working oil to respective actuators, and is a system for reducing the number of hydraulic elements passing through or controlling the working oil to reduce loss due to hydraulic friction. The pump control system ensures a high efficiency of an engine as a loss of a main control valve distributing the working oil is removed. Further, outputs of the actuators can be easily controlled by regulating an amount of the working oil supplied by the pumps.
In this way, a summary of the technology of such a pump control system has been known, but there are problems in that loads of the actuators driven by the pumps are different, and if an over load is applied to any pump, a flow rate of the working oil supplied to the pump becomes insufficient.
The discussion above is merely provided for general background information and is not intended to be used as an aid in determining the scope of the claimed subject matter.